What is URL encoding?

URL encoding (also called percent encoding) converts special characters into a format that can be safely transmitted in URLs.

How URL Encoding Works:

Characters are encoded as a percent sign (%) followed by two hexadecimal digits:

• Space becomes %20 or + (in query strings)
• ! becomes %21
• @ becomes %40
• # becomes %23
• UTF-8 characters like é become %C3%A9

Why URL Encoding is Necessary:

URLs can only safely contain certain characters:

• Letters: A-Z, a-z
• Digits: 0-9
• Unreserved characters: - _ . ~
• Reserved characters (when used for their purpose): : / ? # [ ] @ ! $ & ' ( ) * + , ; =*_

Any other characters must be encoded.

Common Use Cases:

• Query parameters: ?name=John Doe → ?name=John%20Doe
• Search queries: ?q=c++ programming → ?q=c%2B%2B%20programming
• Special characters: ?email=user@example.com → ?email=user%40example.com
• Unicode text: ?city=São Paulo → ?city=S%C3%A3o%20Paulo
• Path segments: /files/my resume.pdf → /files/my%20resume.pdf

Reserved Characters:

These have special meaning in URLs:

• : separates protocol and domain
• / separates path segments
• ? starts query string
• # starts fragment
• & separates query parameters
• = separates parameter name and value

When you need these characters as data (not structure), they must be encoded.

Example:

Original: Hello World! How are you? Encoded: Hello%20World%21%20How%20are%20you%3F

Important Notes:

• URL encoding is reversible (anyone can decode it)
• It's NOT encryption or security
• Different parts of URLs have different encoding rules
• Always encode user input before putting it in URLs
• Modern browsers may show decoded URLs in the address bar